blocks|key|1777182|text|imagealphablending(+$targetImage,+false+);
imagesavealpha(+$targetImage,+true+);|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1777183|都是为了我。谢谢你。|unstyled|1777184|请注意，目标图像需要alpha设置，而不是源图像。|1777185|编辑:完整替换代码。另请参阅下面的答案和他们的评论。这不能保证在任何方面都是完美的，但确实满足了我当时的需求。|1777186|$uploadTempFile+=+$myField[+'tmp_name'+]
list(+$uploadWidth,+$uploadHeight,+$uploadType+)+
++=+getimagesize(+$uploadTempFile+);

$srcImage+=+imagecreatefrompng(+$uploadTempFile+);+

$targetImage+=+imagecreatetruecolor(+128,+128+);+++
imagealphablending(+$targetImage,+false+);
imagesavealpha(+$targetImage,+true+);

imagecopyresampled(+$targetImage,+$srcImage,+
++++++++++++++++++++0,+0,+
++++++++++++++++++++0,+0,+
++++++++++++++++++++128,+128,+
++++++++++++++++++++$uploadWidth,+$uploadHeight+);

imagepng(++$targetImage,+'out.png',+9+);|1777187|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|P|8|@]|9|@]|A|$]]|$1|G|3|H|5|F|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|F|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$B|C]]|$1|M|3|-4|5|F|7|T|8|@]|9|@]|A|$]]]|N|$]]

<pre><code>imagealphablending( $targetImage, false );
imagesavealpha( $targetImage, true );
</code></pre>

did it for me. Thanks ceejayoz.

note, the target image needs the alpha settings, not the source image.

Edit:
full replacement code. See also answers below and their comments. This is not guaranteed to be be perfect in any way, but did achieve my needs at the time.

<pre><code>$uploadTempFile = $myField[ 'tmp_name' ]
list( $uploadWidth, $uploadHeight, $uploadType ) 
 = getimagesize( $uploadTempFile );

$srcImage = imagecreatefrompng( $uploadTempFile ); 

$targetImage = imagecreatetruecolor( 128, 128 ); 
imagealphablending( $targetImage, false );
imagesavealpha( $targetImage, true );

imagecopyresampled( $targetImage, $srcImage, 
 0, 0, 
 0, 0, 
 128, 128, 
 $uploadWidth, $uploadHeight );

imagepng( $targetImage, 'out.png', 9 );
</code></pre>

blocks|key|1562016|text|你为什么把事情搞得这么复杂？下面是我使用的代码，到目前为止，它已经完成了我的工作。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1562017|$im+=+ImageCreateFromPNG($source);
$new_im+=+imagecreatetruecolor($new_size[0],$new_size[1]);
imagecolortransparent($new_im,+imagecolorallocate($new_im,+0,+0,+0));
imagecopyresampled($new_im,$im,0,0,0,0,$new_size[0],$new_size[1],$size[0],$size[1]);|code-block|syntax|javascript|1562018|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Why do you make things so complicated? the following is what I use and so far it has done the job for me.

<pre><code>$im = ImageCreateFromPNG($source);
$new_im = imagecreatetruecolor($new_size[0],$new_size[1]);
imagecolortransparent($new_im, imagecolorallocate($new_im, 0, 0, 0));
imagecopyresampled($new_im,$im,0,0,0,0,$new_size[0],$new_size[1],$size[0],$size[1]);
</code></pre>

blocks|key|1777279|text|我认为这可能会起到作用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1777280|$uploadTempFile+=+$myField[+'tmp_name'+]
list(+$uploadWidth,+$uploadHeight,+$uploadType+)+
++=+getimagesize(+$uploadTempFile+);

$srcImage+=+imagecreatefrompng(+$uploadTempFile+);

$targetImage+=+imagecreatetruecolor(+128,+128+);

$transparent+=+imagecolorallocate($targetImage,0,255,0);
imagecolortransparent($targetImage,$transparent);
imagefilledrectangle($targetImage,0,0,127,127,$transparent);

imagecopyresampled(+$targetImage,+$srcImage,+
++++++++++++++++++++0,+0,+
++++++++++++++++++++0,+0,+
++++++++++++++++++++128,+128,+
++++++++++++++++++++$uploadWidth,+$uploadHeight+);

imagepng(++$targetImage,+'out.png',+9+);|code-block|syntax|javascript|1777281|缺点是图像将被剥离每100%25的绿色像素。无论如何，希望它能有所帮助:)|1777282|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I suppose that this might do the trick:

<pre><code>$uploadTempFile = $myField[ 'tmp_name' ]
list( $uploadWidth, $uploadHeight, $uploadType ) 
 = getimagesize( $uploadTempFile );

$srcImage = imagecreatefrompng( $uploadTempFile );

$targetImage = imagecreatetruecolor( 128, 128 );

$transparent = imagecolorallocate($targetImage,0,255,0);
imagecolortransparent($targetImage,$transparent);
imagefilledrectangle($targetImage,0,0,127,127,$transparent);

imagecopyresampled( $targetImage, $srcImage, 
 0, 0, 
 0, 0, 
 128, 128, 
 $uploadWidth, $uploadHeight );

imagepng( $targetImage, 'out.png', 9 );
</code></pre>

The downside is that the image will be stripped of every 100% green pixels. Anyhow, hope it helps :)

blocks|key|1777358|text|一个可能对某些人有帮助的附加内容：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1777359|可以在构建图像时切换图像混合。在我需要这个的具体情况下，我想把一些半透明的PNG组合在一个透明的背景上。|1777360|首先，将imagelphabling值设置为false，并用透明色填充新创建的真彩色图像。如果imagelphabling值为true，则不会发生任何事情，因为透明填充将与黑色默认背景合并，并导致黑色。|1777361|然后，将imagelphabling值切换为true，并将一些PNG图像添加到画布中，使一些背景可见(即。而不是填充整个图像)。|1777362|结果是一个具有透明背景的图像和几个组合的PNG图像。|1777363|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|M|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|N|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|O|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|P|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|K|$]]

An addition that might help some people:

It is possible to toggle imagealphablending while building the image. I the specific case that I needed this, I wanted to combine some semi-transparent PNG's on a transparent background.

First you set imagealphablending to false and fill the newly created true color image with a transparent color. If imagealphablending were true, nothing would happen because the transparent fill would merge with the black default background and result in black.

Then you toggle imagealphablending to true and add some PNG images to the canvas, leaving some of the background visible (ie. not filling up the entire image).

The result is an image with a transparent background and several combined PNG images.

blocks|key|1777429|text|我用copyimageresample做了一个调整图像大小的函数，比如JPEG/GIF/PNG，而PNG图像仍然保持透明：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1777430|$myfile=$_FILES["youimage"];

function+ismyimage($myfile)+{
++++if((($myfile["type"]+==+"image/gif")+%7C%7C+($myfile["type"]+==+"image/jpg")+%7C%7C+($myfile["type"]+==+"image/jpeg")+%7C%7C+($myfile["type"]+==+"image/png"))+&&+($myfile["size"]+<=+2097152+/*2mb*/)+)+return+true;+
++++else+return+false;
}

function+upload_file($myfile)+{+++++++++
++++if(ismyimage($myfile))+{
++++++++$information=getimagesize($myfile["tmp_name"]);
++++++++$mywidth=$information[0];
++++++++$myheight=$information[1];

++++++++$newwidth=$mywidth;
++++++++$newheight=$myheight;
++++++++while(($newwidth+>+600)+%7C%7C+($newheight+>+400+))+{
++++++++++++$newwidth+=+$newwidth-ceil($newwidth/100);
++++++++++++$newheight+=+$newheight-ceil($newheight/100);
++++++++}+

++++++++$files=$myfile["name"];

++++++++if($myfile["type"]+==+"image/gif")+{
++++++++++++$tmp=imagecreatetruecolor($newwidth,$newheight);
++++++++++++$src=imagecreatefromgif($myfile["tmp_name"]);
++++++++++++imagecopyresampled($tmp,+$src,+0,+0,+0,+0,+$newwidth,+$newheight,+$mywidth,+$myheight);
++++++++++++$con=imagegif($tmp,+$files);
++++++++++++imagedestroy($tmp);
++++++++++++imagedestroy($src);
++++++++++++if($con){
++++++++++++++++return+true;
++++++++++++}+else+{
++++++++++++++++return+false;
++++++++++++}
++++++++}+else+if(($myfile["type"]+==+"image/jpg")+%7C%7C+($myfile["type"]+==+"image/jpeg")+)+{
++++++++++++$tmp=imagecreatetruecolor($newwidth,$newheight);
++++++++++++$src=imagecreatefromjpeg($myfile["tmp_name"]);+
++++++++++++imagecopyresampled($tmp,+$src,+0,+0,+0,+0,+$newwidth,+$newheight,+$mywidth,+$myheight);
++++++++++++$con=imagejpeg($tmp,+$files);
++++++++++++imagedestroy($tmp);
++++++++++++imagedestroy($src);
++++++++++++if($con)+{++
++++++++++++++++return+true;
++++++++++++}+else+{
++++++++++++++++return+false;
++++++++++++}
++++++++}+else+if($myfile["type"]+==+"image/png")+{
++++++++++++$tmp=imagecreatetruecolor($newwidth,$newheight);
++++++++++++$src=imagecreatefrompng($myfile["tmp_name"]);
++++++++++++imagealphablending($tmp,+false);
++++++++++++imagesavealpha($tmp,true);
++++++++++++$transparent+=+imagecolorallocatealpha($tmp,+255,+255,+255,+127);
++++++++++++imagefilledrectangle($tmp,+0,+0,+$newwidth,+$newheight,+$transparent);+
++++++++++++imagecopyresampled($tmp,+$src,+0,+0,+0,+0,+$newwidth,+$newheight,+$mywidth,+$myheight);
++++++++++++$con=imagepng($tmp,+$files);
++++++++++++imagedestroy($tmp);
++++++++++++imagedestroy($src);
++++++++++++if($con)+{
++++++++++++++++return+true;
++++++++++++}+else+{
++++++++++++++++return+false;
++++++++++++}
++++++++}+++
++++}+else
++++++++++return+false;
}|code-block|syntax|javascript|1777431|entityMap^0|2|H|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

I have made a function for resizing image like JPEG/GIF/PNG with <code>copyimageresample</code> and PNG images still keep there transparency:

<pre><code>$myfile=$_FILES["youimage"];

function ismyimage($myfile) {
 if((($myfile["type"] == "image/gif") || ($myfile["type"] == "image/jpg") || ($myfile["type"] == "image/jpeg") || ($myfile["type"] == "image/png")) &amp;&amp; ($myfile["size"] &lt;= 2097152 /*2mb*/) ) return true; 
 else return false;
}

function upload_file($myfile) { 
 if(ismyimage($myfile)) {
 $information=getimagesize($myfile["tmp_name"]);
 $mywidth=$information[0];
 $myheight=$information[1];

 $newwidth=$mywidth;
 $newheight=$myheight;
 while(($newwidth &gt; 600) || ($newheight &gt; 400 )) {
 $newwidth = $newwidth-ceil($newwidth/100);
 $newheight = $newheight-ceil($newheight/100);
 } 

 $files=$myfile["name"];

 if($myfile["type"] == "image/gif") {
 $tmp=imagecreatetruecolor($newwidth,$newheight);
 $src=imagecreatefromgif($myfile["tmp_name"]);
 imagecopyresampled($tmp, $src, 0, 0, 0, 0, $newwidth, $newheight, $mywidth, $myheight);
 $con=imagegif($tmp, $files);
 imagedestroy($tmp);
 imagedestroy($src);
 if($con){
 return true;
 } else {
 return false;
 }
 } else if(($myfile["type"] == "image/jpg") || ($myfile["type"] == "image/jpeg") ) {
 $tmp=imagecreatetruecolor($newwidth,$newheight);
 $src=imagecreatefromjpeg($myfile["tmp_name"]); 
 imagecopyresampled($tmp, $src, 0, 0, 0, 0, $newwidth, $newheight, $mywidth, $myheight);
 $con=imagejpeg($tmp, $files);
 imagedestroy($tmp);
 imagedestroy($src);
 if($con) { 
 return true;
 } else {
 return false;
 }
 } else if($myfile["type"] == "image/png") {
 $tmp=imagecreatetruecolor($newwidth,$newheight);
 $src=imagecreatefrompng($myfile["tmp_name"]);
 imagealphablending($tmp, false);
 imagesavealpha($tmp,true);
 $transparent = imagecolorallocatealpha($tmp, 255, 255, 255, 127);
 imagefilledrectangle($tmp, 0, 0, $newwidth, $newheight, $transparent); 
 imagecopyresampled($tmp, $src, 0, 0, 0, 0, $newwidth, $newheight, $mywidth, $myheight);
 $con=imagepng($tmp, $files);
 imagedestroy($tmp);
 imagedestroy($src);
 if($con) {
 return true;
 } else {
 return false;
 }
 } 
 } else
 return false;
}
</code></pre>

blocks|key|1562230|text|这是我的全部测试代码。对我来说很管用|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1562231|$imageFileType+=+pathinfo($_FILES["image"]["name"],+PATHINFO_EXTENSION);
$filename+=+'test.'+.+$imageFileType;
move_uploaded_file($_FILES["image"]["tmp_name"],+$filename);

$source_image+=+imagecreatefromjpeg($filename);

$source_imagex+=+imagesx($source_image);
$source_imagey+=+imagesy($source_image);

$dest_imagex+=+400;
$dest_imagey+=+600;
$dest_image+=+imagecreatetruecolor($dest_imagex,+$dest_imagey);

imagecopyresampled($dest_image,+$source_image,+0,+0,+0,+0,+$dest_imagex,+$dest_imagey,+$source_imagex,+$source_imagey);

imagesavealpha($dest_image,+true);
$trans_colour+=+imagecolorallocatealpha($dest_image,+0,+0,+0,+127);
imagefill($dest_image,+0,+0,+$trans_colour);

imagepng($dest_image,"test1.png",1);|code-block|syntax|javascript|1562232|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Here is my total test code. It works for me

<pre><code>$imageFileType = pathinfo($_FILES["image"]["name"], PATHINFO_EXTENSION);
$filename = 'test.' . $imageFileType;
move_uploaded_file($_FILES["image"]["tmp_name"], $filename);

$source_image = imagecreatefromjpeg($filename);

$source_imagex = imagesx($source_image);
$source_imagey = imagesy($source_image);

$dest_imagex = 400;
$dest_imagey = 600;
$dest_image = imagecreatetruecolor($dest_imagex, $dest_imagey);

imagecopyresampled($dest_image, $source_image, 0, 0, 0, 0, $dest_imagex, $dest_imagey, $source_imagex, $source_imagey);

imagesavealpha($dest_image, true);
$trans_colour = imagecolorallocatealpha($dest_image, 0, 0, 0, 127);
imagefill($dest_image, 0, 0, $trans_colour);

imagepng($dest_image,"test1.png",1);
</code></pre>

blocks|key|1777657|text|注意传递给imagecopyresampled函数的源图像的width和height值。如果它们大于实际的源图像大小，则图像区域的其余部分将被黑色填充。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1777658|entityMap^0|5|I|U|5|10|6|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|O|8|@]|D|@]|E|$]]]|G|$]]

Pay attention to the source image's <code>width</code> and <code>height</code> values which are passed to <code>imagecopyresampled</code> function. If they are bigger than actual source image size, the rest of image area will be filled with black color.

blocks|key|1562504|text|我把ceejayoz和Cheekysoft的答案结合起来，给了我最好的结果。如果没有imagealphablending()和imagesavealpha()，图像就不清晰：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1562505|$img3+=+imagecreatetruecolor(128,+128);
imagecolortransparent($img3,+imagecolorallocate($img3,+0,+0,+0));
imagealphablending(+$img3,+false+);
imagesavealpha(+$img3,+true+);
imagecopyresampled($img3,+$srcImage,+0,+0,+0,+0,+128,+128,+$uploadWidth,+$uploadHeight);
imagepng($img3,+'filename.png',+9);|code-block|syntax|javascript|1562506|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I combined the answers from ceejayoz and Cheekysoft, which gave the best result for me. Without imagealphablending() and imagesavealpha() the image is not clear:

<pre><code>$img3 = imagecreatetruecolor(128, 128);
imagecolortransparent($img3, imagecolorallocate($img3, 0, 0, 0));
imagealphablending( $img3, false );
imagesavealpha( $img3, true );
imagecopyresampled($img3, $srcImage, 0, 0, 0, 0, 128, 128, $uploadWidth, $uploadHeight);
imagepng($img3, 'filename.png', 9);
</code></pre>

The following PHP code snippet uses GD to resize a browser-uploaded PNG to 128x128. It works great, except that the transparent areas in the original image are being replaced with a solid color- black in my case. 

Even though <code>imagesavealpha</code> is set, something isn't quite right.

What's the best way to preserve the transparency in the resampled image?

<pre><code>$uploadTempFile = $myField[ 'tmp_name' ]
list( $uploadWidth, $uploadHeight, $uploadType ) 
 = getimagesize( $uploadTempFile );

$srcImage = imagecreatefrompng( $uploadTempFile ); 
imagesavealpha( $targetImage, true );

$targetImage = imagecreatetruecolor( 128, 128 );
imagecopyresampled( $targetImage, $srcImage, 
 0, 0, 
 0, 0, 
 128, 128, 
 $uploadWidth, $uploadHeight );

imagepng( $targetImage, 'out.png', 9 );
</code></pre>

Can PNG image transparency be preserved when using PHP's GDlib imagecopyresampled?

下面的PHP代码片段使用GD将浏览器上传的PNG大小调整为128x128。它工作得很好，除了原始图像中的透明区域被替换为纯色-在我的情况下是黑色。即使设置了imagesavealpha，还是有些地方不太对劲。在重新采样的图像中保持透明度的最好方法是什么？$uploadTempFile = $myField[ 'tmp_...

问当使用PHP的GDlib图像拷贝采样时，PNG图像的透明度能被保留吗？
EN

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问当使用PHP的GDlib图像拷贝采样时，PNG图像的透明度能被保留吗？
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